2/17High-rpm engines demand quality parts, which is why we spec'd this engine with a good steel Scat crank and rods and Mahle forged pistons.

While car crafters are more into horsepower than math equations, the one formula most performance enthusiasts are intimate with is: horsepower = torque x rpm 5,252.

Big engines rely on lots of displacement to make torque and horsepower, but with smaller engines, the approach is to rev it high. Push the torque higher in the rpm band, and you'll make more horsepower. As an example, 400 lb-ft at 4,000 rpm equates to 304 hp. But that same 400 lb-ft at 6,500 rpm is a smokin' 495 hp.

Among the little V-8 engines, the most popular has to be the 302ci small-block Ford. While the rest of the world is building ever-larger engines, the little Blue Oval pushrod 5.0L continues to surge in popularity. Lately, Car Craft has been playing around with different 302 Ford combinations, so this time we decided to punch up the displacement a little while still relying on rpm to deliver a big horsepower number. While 347ci strokers are OK, we decided to go with the shorter 3.25-inch arm and build a 331ci screamer.

Our goal was aggressive yet simple: build a normally aspirated pump-gas 331ci small-block Ford that could make 1.5 hp per cubic inch that wouldn't explode all over the place. You've probably already skipped down to the dyno test, so you know we came really close 500 with 496 hp at 7,400 rpm that is dead reliable.

CC contributor Tim Moore built this engine, and it's currently scheduled as the motorvation for his Dan Gurney Trans-Am-tribute '67 Cougar. Just the thought of spinnin' this small-block up to 7,500 rpm and bangin' Fourth gear coming off Turn 6 at Willow Springs sounds like a great way to spend a Saturday afternoon.

Building BlocksThe 331ci small-block Ford is a classic stroker package that combines an excellent bore and stroke combination that can withstand the kind of rpm abuse Moore had planned. The stock 302 Ford small-block combines a 4.00-inch bore with a 3.00-inch stroke. To get to 331 inches, Scat offers a forged steel crank with a slightly longer 3.25-inch stroke that matches nicely with a 4.030-inch bore.

Heads And CamThe one place "bigger is better" works is where the goal is lots of horsepower at high engine speeds. Since Moore is aiming for engine speeds in excess of 7,000 rpm, he was less concerned with low-speed torque. That's why he decided on a set of Air Flow Research 205cc runner wedge heads for his 331 spinner. AFR offers four different intake-port-volume cylinder heads, from the high-velocity 165cc and 185cc heads to the larger 205 and top-billing Outlaw 225cc monsters. Moore decided to go with the 205cc Outlaw castings that AFR claims will flow more than 300 cfm above 0.550 inch of valve lift on the intake. Packaged with 2.08/1.60-inch intake and exhaust valves, these heads can get with the program, especially with their much more efficient exhaust ports AFR says can generate 225-cfm-plus numbers above 0.500-inch lift. Taking nothing away from the impressive intake flow numbers, it's important to have good exhaust ports if you want to make serious horsepower. With strong exhaust port flow we can minimize the amount of additional camshaft exhaust duration necessary to make maximum horsepower.

6/17Since Moore fully intended to spin the jeebers out of his 331, he searched out a '68 Mexican casting that offers thicker main webbing and caps for a little more strength. These blocks can be identified by the casting Hecho en Mexico (Made in Mexico) in the lifter valley.Cerveza es bueno!

Moore went with a Comp Cams mechanical roller, since there's really no reason for a hydraulic cam to be spinning more than 7,000 rpm. The advertised specs look especially big at 274/280 for a 331ci engine, but at 0.050-inch tappet lift, the numbers come in at 236/242 degrees. To be technically accurate, we also have to subtract 1/2 degree per 0.001 inch of lash that is required for clearance to compare these mechanical lifter numbers with what most enthusiasts recognize as hydraulic cam numbers. With 0.16 inch of intake lash, subtract 8 degrees from the 0.050 duration numbers, which reveals the true specs of 228 degrees of duration at 0.050-inch tappet lift. We combined good Comp mechanical roller lifters, 0.080-inch-wall-thickness Comp Hi-Tech pushrods, and a set of 1.6:1 Pro Magnum roller rockers, tied in with the ARP 7/16-inch rocker studs and AFR roller cam valvesprings-and never once experienced valve float difficulties. This immediately motivated us to consider swapping to a set of 1.7:1 roller rockers, but we ran out of time before we could take this engine to that next level.

CAM SPECS

Camshaft

Duration (Advertised)

Duration (at 0.050)

Lift

LASH

Lobe Separation

Comp roller (intake)

274

236

0.602*

0.016-inch

110

35-770-8 (exhaust)

280

242

0.608*

0.018-inch

7/17There is a small amount of block-clearancing necessary to create room for the longer stroke and especially for the Scat H-beam rods. The bottom of the cylinder bores only needs a minor amount of trimming.

These are gross valve-lift numbers that do not take into account the lash. Subtracting the lash creates a net intake lift of 0.586 inch and an exhaust lift of 0.590 inch. These numbers are based on a 1.6:1 rocker ratio.

Test DayOur first pull to check the air/fuel ratio indicated where we were headed when torque was still climbing at 5,000 rpm. We ran a Holley 750-cfm Street HP carburetor and an Edelbrock Super Victor single-plane intake manifold, and the fuel curve was incredibly steady allowing us to concentrate on optimizing the package. With peak torque at 5,600 rpm, the horsepower peaked at 7,400 rpm with 480 hp. Not only is this almost directly on top of our 1.5hp/ci goal, but it's also very repeatable with several runs at that level. Timing and jetting changes produced a few minor improvements, and then we bolted on a Wilson 1-inch open spacer that finally helped us kick the peak power up to 496 hp.

8/17Moore also included a TFS-built main-cap girdle that will clear the Milodon oil pan and pickup assembly. The girdle ties all the main caps together to reduce crank movement, especially at high engine speeds.

With an 1,800-rpm powerband between peak torque and peak horsepower running a solid 1.5 hp/ci and plenty of durability, there's little more we could ask of this stroked-block Ford other than maybe 4 more horsepower so we could claim 500. In post-testing discussion with AFR's Tony Mamo, he suggested the 185cc Outlaw Street heads would probably have made the same peak power while also pumping up the midrange torque slightly. Here's a case where being a little more conservative might have made even more power. How can you lose on a deal like that? We also have to admit that in the car, these numbers will drop a little after fitting the engine with chassis-style heads, an accessory drive, an air cleaner, and other accouterments that must accompany a street-driven engine. But the fact remains that this is one stout small-block Ford.

Dyno TalesTest 1 is the initial test as configured in the initial buildup of the engine, including the AFR 205cc heads, Comp mechanical roller cam, Edelbrock single-plane Victor intake, 750-cfm Holley HP carburetor, and 13/4-inch headers with open exhaust.

Test 2 added a 1-inch open spacer to the intake manifold, with all other components remaining the same.

9/17Lubrication is important, and since this engine will also see high lateral-g turns, Moore went with a Milodon road race oil pan to ensure the pickup is always submerged in fresh oil, no matter what the car is doing. We also included a high-strength ARP oil pump drive to overcome a classic small-block Ford weak spot.

TEST 1

TEST 2

RPM

TQ

HP

TQ

HP

3,{{{600}}}

368

252

367

251

3,800

375

271

371

268

4,000

378

288

378

288

4,{{{200}}}

385

308

384

307

4,400

390

327

390

326

4,600

395

345

393

344

4,800

400

366

397

363

5,000

408

389

{{{405}}}

393

5,200

414

410

408

404

5,400

416

428

412

423

5,600

416

443

413

440

5,800

416

456

412

455

6,000

410

468

411

469

6,200

406

479

407

480

6,400

399

486

398

485

6,600

388

488

389

489

6,800

375

486

377

488

7,000

366

488

366

488

7,200

359

493

359

493

7,400

350

493

352

496

Peak

416

493

413

496

Average

390.3

411.2

391.3

412.2

12/17What is not well known is that AFR raises the exhaust ports on these heads by 0.125 inch, which is one reason the exhaust ports work so well.

PARTS LIST

DESCRIPTION

PN

SOURCE

PRICE

AirFlow Research 205cc heads

1450

Buyafr.com

$1,838.19

ARP head studs

154-4203

{{{Summit}}} Racing

149.95

ARP intake bolts

454-2001

Summit Racing

31.95

ARP flywheel bolts

{{{200}}}-2802

Summit Racing

10.95

ARP balancer bolt

150-2501

Summit Racing

20.95

ARP oil pan stud kit

254-1901

Summit Racing

42.95

ATI balancer

918895

Summit Racing

369.95

Autolite spark plugs, race plugs

AR-3923

Summit Racing

21.52

Clevite main bearings

MS590H

Summit Racing

69.95

Clevite rod bearings

CB634H

Summit Racing

10.25

Clevite cam bearings

SH1321S

Summit Racing

21.69

Comp Cams street roller cam kit

CL35-770-8

Summit Racing

599.95

Comp Cams roller rockers, 1.6:1

1332-16

Summit Racing

285.95

Comp Cams timing chain set

3135

Summit Racing

69.95

Comp Cams pushrods

7937-16

Summit Racing

153.39

Edelbrock Super Victor intake

29285

Summit Racing

389.95

{{{Ford}}} Mexican 302 block

used

Swap meet

{{{300}}}.00

Holley 750-cfm HP carb

80528

Summit Racing

663.95

Mahle piston, 4.030-inch bore

SBF165030F06

Summit Racing

680.95

Milodon oil pan

31600

Summit Racing

349.95

Milodon oil pump

18800

Summit Racing

78.69

15/17The induction side of things consisted of an Edelbrock Super Victor single-plane and a Holley 750-cfm Street HP carburetor. We also improved power with a 1-inch open spacer, but that may be difficult to package under a stock hood. Also notice that this particular Super Victor is fitted with EFI bungs, since Moore is toying with the idea of eventually converting to EFI. We also used a steel-gear MSD distributor to light the fire.